Method of making enameled containers



April 1942- J. A. BoHNsAcK 2,281,407

METHOD OF MAKING ENAMELED CONTAINERS Filed April 25, 1939 4 Sheets-Sheet 1 n vvmox ATTORNEY.

April 1942- J. A. BoHNsA'cK "BTHOD OF MAKING ENAMELED CONTAINERS Filed April 25, 1959 4 Sheets-Sheet 2 April J. A. BOHNSACK 2,231,407

"ETHOD OF MAKING ENAMELED CONTAINERS Filed April 25, 1939 4 Sheets-Sheet 5 II III) III IINVENTOR.

ATTORNEY.

Patented Apr. 28, 1942 METHOD OF MAKING ENAMELED CONTAINERS John A. Bohnsack, Youngstowm'flhio, assignor,

by mesne assignments, to Porcelain Steels, Inc., Cleveland, Ohio, a. corporation of Ohio Application April 25, 1939, Serial No. 269,946

2 Claims. (c1. 29-148.?!)

This invention relates to containers of the tank or range boiler type .and particularly to range boilers coated with vitreous enamel inside, or inside and outside.

In my co-pending patent application, Serial Number 262,117, filed March 16, 1939, I have illustrated and described an enameled sheet metal tank of the range boiler type comprising a tubular body and heads welded to opposite ends of the body. The enameled tank or boiler of that application has head flanges overlapping the body wall and welded thereto by an electric rollwelding process.

In the enameled tank or range boiler of the instant application, the heads are welded to the body by an electric flash welding process.

The most economical method for the construction of tanks or range boilers is, as is Well known, to fabricate the walls thereof from joined pieces of sheet metal. Tanks or range boilers have been proposed in which the pieces are joined by riveting, or by welding, and coated with vitreous or porcelain enamel of the fired fused type, but such enameled tanks, particularly of the range boiler type which, in use, contain hot water or other corrosive fluid and are subject to internal pressure and to differentials of temperature in different parts thereof, have not been successful because of the inevitable development of cracks in the enamel particularly at the junctures of the pieces. The primary purpose of enameling a tank or range boiler is to prevent corrosion and ultimate perforation of the wall by the corrosive action of water or other fluid contained therein. The enamel coat must therefore be solid and complete, because a single crack or pin hole imperfection in the enamel will exposethe sheet metal wall to corrosion and develop a leak in the wan.

Upon the homogeneous, principal surfaces of the tank or range boiler wall, a solid complete coating of vitreous enamel can be formed without difficulty; but to construct the junctures of the pieces so tat the enamel will form solidly and evenly thereon and adhere thereto and not crack in use, as referred to, presents a One cause of the cracking of th joints in a tank or range boiler oi prising a body and heads on the endsis the fact that when the tank or subjected to internal pressure in 1 tend to bend or bulge outwardl mediate portions which puts re made.

relatively with a hinging or spreading movement which, however slight, will crack the vitreous enamel covering the joint.

The junctures of the parts must therefore be of such character as to join the adjacent pieces integrally throughout the juncture to prevent such relative movement and enamel cracking. Rivets have failed in this respect. Welding has been proposed, but welding itself presents other difliculties.

If the welds at the joints are made by torch welding or arc welding processes, the metal at the juncture tends to be porous and contain impurities, which makes diflicult the formation of a solid complete coat of enamel over the juncture.

In my aforesaid pending patent application, I have overcome these dimculties in a tank or range boiler of the type in which the heads have flanges overlapping the ends of the main body, by roll welding the flanges to the body by a weld which integrally joins the flange and body all the way to the extreme axial end of the overlap of the flange and body. The juncture is therefore integral and prevents relative movement of the parts,v and may be readily covered by a solid enamel coat.

In the tank or range boiler of the instant ,application, the parts are joined by flash welding which effects a completely integral juncture not subject to relative movement of the joined parts. It has been discovered, after long experimentation, that a flash welded joint between sheet metal pieces, after the flash fin has been tooled ofi, provides a metal surface of such pure and solid metal that vitreous enamel will readily adhere thereto, and form a continuous solid coat thereover.

In making a tank or range boiler by the flash welding process, and particularly when it is of the conventional type comprising a tubular bodyand a head Welded on each end of the body, the last or second welded head makes of the tank or boiler a closed container, except for the relatively small threaded omnings to which conduit connections are to be made in use, and therefore the removal of the flash fin of the second welded head, to surface the juncture so that it will take enamel, presents an additional problem, which has been solved in the boiler of the present application as will hereinafter be set forth.

Another cause for the cracking of the enamel on a tank or range boiler is that the parts from which it is fabricated bend or yield. under internal pressure. This occurs in a tank of the type having heads secured to the opposite ends of a These problems and difficulties have been overcome in the boiler of the present application as will hereinafter be set forth.-

It is among the objects of this invention: To provide generally an improved container of the tank or range boiler type;

To provide an improved container of the tank or range boiler type having a. solid and complete coat of vitreous enamel on the walls thereof; To provide an improved container of the tank or range boiler type formed from a plurality of sheet metal pieces secured together by welded junctures of such character that vitreous enamel will form solidly and completely thereover and adhere thereto;

To provide a container of the tank or range boiler type formed of a plurality of sheet metal pieces flash welded together in an improved manner;

To provide an improved method of making a container of the tank or range boiler type;

To provide an improved method of making an enameled container of the tank or range boiler type from pieces of sheet metal welded together;

To provide an improved spud or threaded conduit connection for containers of the tank or range boiler type.

Other objects will be apparent to those skilled in the art to which my invention appertains.

My invention is fully disclosed in the following description taken in connection with the accomnecting the other conduits to the boiler;

Fig. 3 is a view similar to Fig. 2 illustrating a spud conduit connection to the side of the boiler of Fig. 1 and which may be used for the other" conduit connections to the boiler, Figs. 2 and 3 being modifications which may alternatively be used as desired;

Fig. 4 is a view illustrating a step of method of making the spud conduit connection of Fig. 3;

flash welding a head upon the body of the range boiler of Fig. 1 and indicating the welding of the other head on the body;

Figs. 13 and 14 are fragmentary views illustrating respectively a part of the head and body before and after welding;

Fig. 15 is a view in some respective diagrammatic illustrating in simplified form an apparatus for performing the method .step of tooling oi! the flash fln on the inside of the boiler resulting from flash welding the first head;

Fig. 16 is a fragmentary sectional view taken from the plane 16-46 of Fig. 15;

Fig. 5 is a view similar to Fig. 4 illustrating a 1 modification;

Figs. 6 and 7 are respectively elevational and cross-sectional views of the tubular body of the boiler of Fig. 1 as it appears in the process of making the boiler;

Fig. 8 is a view partly in section and insome respects diagrammatic of an apparatus for performing a die drawing operation on the boiler bodyof Figs. 6 and 7;

Fig. 17 is a view having the above stated characteristics of Fig. 15 but illustrating the step of .method of tooling ofi the interior flash fln resulting from flash welding the second head on the range boiler body, and also illustrating a method of removing both exterior' flash weld flns;

Fig. 18 is a sectional view taken from the plane |8l8 of Fig. 17 with parts behind the plane of section omitted for simplicity;

-Fig. 19 is a fragmentary view similar to a part of Fig. 1'! illustrating a modification in the form of a tool of that figure.

Referring to Figs. 1 to 3 inclusive, which illustrate structural features of the enameled range boiler of my invention, I havev shown in Fig. l the complete boiler. It comprises .a tubular sheet metal main body or wall I, preferably of circular cross-section, and having 0 its upper and lower ends'respectively, heads 2 and 3 also of sheet metal, the heads having tubular flanges 4 and! welded to the opposite ends of the body I by an electric flash welding process to be described. As is well known, boilers of this class are subjected to internal pressure and therefore the heads 2 and 3, unless they are hemispherical in form, tend to bend or bulge outwardly, which will crack an enamel, coat thereon, and to resist such bending the heads 2 and 3- are made from thicker sheet metal than the body I, although the flange portions 4 and 5 thereof are of substantially the same thickness as the body I at the flash weld.

The flash welds are indicated diagrammatically by the dotted lines 6 and I.

It will be understood that these flash welds join the metal of the flanges 4 and 5 with the body I so completely integrally that the juncture is not visible and that therefore the dotted lines 6 and 1 merely indicate the approximate locality of the welds.

The lower head 3 tapers downwardly all the way to an opening at its center, for a purpose to be described in connection with the process of applying'and forming'an enamel coat thereon, and the center of this head as shown in Fig. 2 and indicated in Fig. l, terminates in an outwardly protruding hollow neck 8. A spud 9 is welded to the neck 8 and has exterior threads 10 thereon. A conduit connection nipple ll,'t o

be referred to later, is mounted on the spud 9 by may be used in the method ofmaking both the 4 upper and lower boiler heads;

Figs. 10 and 11 are fragmentary views'illustrating steps of method in the. making of the boiler heads and operations performed upon the head of Fig. 9;

Fig. 12 is a view in some respects diagrammatic illustrating in simplified form an apparatus for a coupling nut l2. By this construction, a pipe or conduit l3 threaded into the nipple ll communicates with the interior of the boiler, through the lower head.

The conventional circulating system for range boilers, particularly when usedas a supply of hot water for domestic purposes, calls for a pair of conduit communicating connections through the upper head of the boilerfand in some cases, a pair of lateral conduit connections through the side wall of the boiler, besides the single conduit connection above described through the bottom press formed upwardly from the intermediate or conduits 20 and 2L Similarly necks 22 and 23 are provided extending outwardly from the main body I, and nipples 2d and 25 and associated coupling nuts 26 and 27! provide for connection with communicating pipes or conduits 28 and 29. The five conduit connections above referred to may all be alike and any suitable number or arrangement or location thereof may be provided.

As shown in Fig. 2, the spud 9 is provided with a tubular flange 30 thereon which is fiash welded to the outer end of the neck 8. i

If preferred, the modification shown in Figs. 3 and 4 may be used, Fig. 3 being referred to one of the side wall conduit connections. construction is employed for the spud connection, the side wall having the said external thread, in this case 33,

is provided with a conical face 34, and with a cylindrical end portion 35, the latter substantially fitting the periphery of the perforation 3|.

To weld this spud 32 in place, the cylindrical portion 35 is inserted in the perforation 3| with the conical shoulder 34 in the side wall thereof.

The lower head 3 has welded thereto a plu-' rality, such as three, downwardly extending legs 4340-40. These legs are preferably formed of Fig. 3 if that be employed), the outside coat 42 extends all the way to the threads (or to vided with a The central opening through the spud terminates outwardly as at Ml, Fig. 2 (and 45, Fig. 3) in a tapering or conical surface and the enamel coat forms thereover also as at 43.

Before securing the nipple on the spud, a packgasket sealingly upon the enamel at 43 by the coupling nut, the nipple preferably being proconical bead 48 which forces the packing washer 44 down into the conical termination of the opening and upon the enamel at 46, as plainly shown in Figs. 2 and 3.

By this means the inside surface of the boiler, including the opening through the spud, is in through the upper head 2, may be formed to permm the conduit to extend through the nipple a single uncoated spot on the inside surface will be vulnerable to the corrosive action of hot water therein and will ultimately developa leak. Nothing less than a completely perfect and durable enamel coat will sufiice.

These features will be briefly discussed and this will be followed by a description of steps of the process of making the boiler by which these characteristics and features are embodied in the finished boiler.

extensive experimentation that if the weld at such a juncture be so located that the enamel coat must form thereover on 'a substantial surface area thereof, the best type of welded juncture is a flash welded juncture. Any other type, such as torch welding or electric arc welding, will leave the material at the juncture in such a condition physically and chemically, that it is diflicult to form a solid enamel coat thereon.

Inorder to successfully flash weld the flanges 4 and 5 of the heads 2 and 3 to the ends of the body wall I, these flanges and the body wall'xnust be of substantially the same wall thickness and also of the same diameter. I

It is desirable, for the reason stated above, that the main portion of the heads be of thicker material than the flanges to prevent bending and enamel cracking, and. therefore a reduction of thickness of. the metal of the head must be effected at the zone of the wel After the flash welds have been made, the fla h or fin which inevitably projects laterally from any flash weld, must be tooled off down to the solid metal,otherwise the enamel coat will not form completely thereover or adhere thereto.

When the spuds are welded on, if there are any projections, irregularities or roughness at the welded junctures thereof, they may readily be removed by any suitable tooling operation, inasmuch as these junctures are accessible through the openings of the spuds themselves. When the metal parts of the boiler have been completely fabricated the wet enameling slip, which as is Well known, may be a mixture of granular glass or frit and water and other ingredients, may then be applied to the walls of the boiler by immersing the boiler thereinand rotating it if desired. The tank may then be withdrawn from the mixture and disposed in upright position and the surplus will drain off downwardly throughthe neck 8 in the lower head, and it is for this purpose that this lower head tapers all the way outwardly ,through the neck in the coating of slip may then be dried in any suitable manner with or without heat, and the dried slip, if any, remaining on the external threads of the spud may be removed byrunning a nut or die thereover, or by brushing them with a brush.

The firing of the dried enamel slip coat may be performed in the usual manner.

Coming now to some of the more important steps of the process of fabricating the metal parts of the boiler, I have shown in Figs. 6 and '1 the main body I as formed into hollow cylindrical forni from sheet metal, the edges being welded together as at 50 by the electric flash welding operation. The flash fins, internal and external are then removed. These operations are all well known and have been practiced in the flash welding of barrels and other containers having a longitudinal flash welded seam..

The thickness of the wall of the body is, of course, determined by metal from which it is made, but I have found that to predetermine itsdiameter to be the same as that of the flanges of the heads, above referred to, and to insure that it will be truly "circulet in cross section so as not to bend under in-' ternal pressure and crack the enamel coat, it is prefer-able to form it with a slightly excess diameter and then die draw it'down to the requisite diameter and circular form. In Fig. 8 I have illustrated, in some respects diagrammatically, an apparatus for performing this die drawing of the ody. l

the thickness of the chosen ders by conduits 63-63 and out to the source by a conduit 64. The said communication of presform of a funnel. The

- body I is formed and to the same diameter as the drawn diameter of the body; The skirt may,

rocable therein connected to piston rods projecting upwardly through the frame 5|, and

A main frame 5| has a circular centering head 52 thereon having an upwardly extending annular circular flange 53 reduced in diameter to provide a shoulder 54. The flange 53 and shoulder 5 are proportioned so that an end of the body I may be telescoped over the flange and rest upon the shoulder. in upright position.

Secured to the underside of the frame 5| is a pair of fluid pressure cylinders 55-55 preferably of the hydraulic type having pistons 56-565r1ecir5);

having secured to their upper ends a drawing die 58 in the form of. an annulus, the opening 55 in the annulus being accurately formed to a circle and to the desired diameter of the body.

A valve device 60 controls the admission of fluid pressure from a pressure source through a conduit 6| to the upper ends of the cylinders 55 by way of conduit 62-52 and the concurrent exhaust of fluid from the lower ends of the cylinsure is efiected at the valve 60 by moving a handle 65 thereof to the position shown. By moving the handle to another position pressure may be admitted to the lower ends of the cylinders and exhausted from the upper ends thereof, all in a well known manner.

At the start of the operation, the die 58 is moved to the upper broken line portion 58A by upward movement of the pistons 56-56 and the body I is placed on the centering head 52. The die 53 is then drawn downwardly and moved with a drawing operation over the outside of the body, an intermediate position therefor being shown in solid line, and at the lower end of its stroke, the die 58 moves beyond the lower end of the body I resting on the shoulder 52, to the lower broken line position 5813. I The body I may'then be removed and the operation repeated for other bodies.

The seam weld 50 being aflash welded seam, there is no liability that this drawing operation will spread or open the seam.

The necks or perforations may now be formed in the wall and the spuds welded thereto, as described above.

In Figs. 9, 10 and 11, I have illustrated some of the steps of making the heads 2 and 3 of the boiler, Fig. 9 illustrating particularly the head 3, although the steps to be described may be employed also in the making of the head 2.

The head is press formed as stated from metal thicker than that from which the body is formed, and as shown, the head is generally of cup form. When first formed, the head has a skirt 56 the outer end of which terminates in a laterally extending flange 61, and in the process of forming the head, the skirt in the outer portion thereof, as at 58, is drawn to a reduced thickness substantially that of the sheet metal from which the in a first press forming operation, be of the same thickness as the rest of the head and of the flange 51, and then the head may be gripped by the flange 51 to draw the skirt portion 56 m the desired thinner wall thickness, and to more exactly determine its diameter.

The head is then placed in a shearing die, prising relatively reciprocable annular shearing elements 59 and 10, the element 59 having a shoulder ll upon which the end of the skirt portion 53 may rest and having a cylindrical portion I2 fitting the inside of the skirt portion 68. The shear element III has an opening I3 therein fitting the outside of the skirt portion 68.

The two shear elements are reciprocated towards each other and the flange 61 is sheared off as shown in Fig. 11, leaving the skirt portion 6t as a tubular flange on the periphery of the head. The shearing operation leaves the skirt portion 68 with the desired thickness and diameter, and may in fact be relied upon to further true up the thickness and diameter. The force exerted on the skirt portion by this operation, forces the extreme end edge thereof, as at 14, against the shoulder ll of the die element 89 thereby squaring oil the end and removing the roundness from this end which may have formed thereon, as at 15, Fig. 9, when the flange 61 was formed. As stated above, both heads 2 and 3 may be provided with reduced thickness skirt portions 68 by this process.

The heads are then flash welded to the opposite ends of the body I. A part of this process is illustrated in Figs.' 13 and 14. As shown in Fig. 13, the said reduced thickness skirt portion 68 is disposed in abutting relation with the end of the, body i; then electric current is passed through the points of engagement indicated by the line I6 and the flash welding are forms theremetal melts or burns away from considerable distance back from between. The both pieces a their orig nal in some cases being as much as one and one half times the thickness of the metal, the zone to which the metal is burned away being indicated in broken lines at TI and, 78. The two parts are then abruptly pressed together to effect the weld, the parts then taking up the positions shown in Fig. 14. The remaining portion of the reduced thickness skirt of the head may now be again referred to as the flange d for the head 2, or the flange for the head 3. The resulting flash or fin at the weld is shown at it on the outside and at 88 on the inside.

Both of these flash fins i9 and 80 must be removed by tooling operations which will be described. The flash 88 on the inside being relatively inaccessible is caused'to be of lesser extent than the flash 79 on the outside, by subjecting the interior of the body and head to air pressure while the flash welding is going on.

In Fig. 12 is illustrated, in some respects diagrammatically, an apparatus for performing this flash welding operation. The head 3 having the central spud opening, is welded on first and the head 2 last. At 8I'is a cradle in which the body I is supported. The end of the body opposite to the head to be welded is closed and sealed air tight, by a cover 82 which rests 'in anannular notch 83 in a rear head 84 of the apparatus.

The head 3 is seated in a ring 85 on a head 86 reciprocable in ways 87-81. To hold the head 3 in the ring 85 any suitable means may be provided. That illustrated diagrammatically comprises a cap 88 having connected thereto a threaded stem 89 which projectsthrough a perforation in a' bridging element 90 of the head 85 and has a nut 91 threaded thereon beyond the bridge. When the nut is turned, the stem 89 and cap 88 draw the head 3 securely into the ring 85 and seat it therein, thereby attaching the head 3 to the reciprocatory head 86.. The cap 88 seals the spud opening air tight.

The head 85 has a cam follower roller 92 therepoints of engagement, this distancethreaded on the head spud and on engageable with a rotary cam 93 on a shaft 94. 7

The roller 82 is normally seated in a notch 95 of the cam, that is to say, when the head 86 is in its fully retracted position illustrated.

One of the lateral spud connections to the boiler is closed and sealed by a cap 96 threaded on the spud and the, other spud connection has a flexible hose 9? sealedly connected thereto.

The hose 9! is connected to a reservoir -98 of compressed air through an automatic valve device 98 and air under pressure is applied to the reservoir 98 by a compressor I00. The automatic valve device 99 is provided to maintain, within the boiler being welded, air pressure at a. constant value. Some of the air passing into the boiler through the device 99 and the conduit 91 will leak out and a considerable portion thereof will flow outwardly radially through the gap and are at the zone of welding, and in variable amount as the weldingprocess proceeds. A valve device 99 is chosen which will maintain the internal pressure substantially constant in spite of this variation of leakage. Such devices are well known and any suitable or well known device may be employed.

Welding current is conducted to the head 3 and the body I in any suitable manner. The means shown comprises a transformer secondary M, the pposite terminals of which are'connected respectively to the head 3 and body I adjacent the edge I02 of the body and the edge I03 of the head, the secondary being energized by a transformer primary I. Preferably a plurality, such as three, transformer secondaries will be em- Dloyed connected to the body and head at circumferentially spaced portions. Two. other transformer secondaries are indicated in the drawing by the terminal wires IOIA and IOIB. The electrical connection between the transformer secondaries and the head 3 and body i, may be made by pressure contact of electrodes therewith, not shown.

In operation, the transformers are energized and the shaft 94 of the cam 93 is turned clockwise as viewed in the drawing, and acting upon the cam follower 92 propels the head 85 toward theleft, moving the edges H13 and I 02 into engagement with each other. The electric are forms therebetween, as described in connection with Figs. 13 and 14, melting away the metal at the edges; the cam 93 feeds the head 3 toward the body I to maintain the arc and at the end of the feeding operation a projection M5 on the cam abruptly pushes the head against the body with an upsetting action, and thereafter the current is discontinued by de-energization of the transformers. The upsetting action forms the fins at 19 and referred to, and the effect of the air pressure within the boiler is to cause most of the fin to form on the outside, as shown in Fig. 14. I have found that a suitable air pressure for this purpose is approximately 15 lbs. per square inch. The air pressure may be maintained within the boiler concurrently with the heating of the metal, or may be introducedjust prior to the upsetting operation.

By maintaining the air pressure constant as described, I have found that not only will a smaller fin form, but it will be more regular and in the manner to be deable means which will occur to the art,

rangement the spindle II4 H8 is provided having at openingof the spud the body I to the cap 82 and the cap to the head 84, one such means being shown for the head 3 at the right hand end of the boiler.

The head 2 may be welded on by an operation like that described above, in which case the head 3, now welded on, will be seated in the head 84, as indicated at 3 in broken lines, and the spud outlet therefrom may be sealed air tight by a cap I85, and a device or devices corresponding to the the body and two heads make a closed container except for the relatively small openings through has been welded on, as de- The body I, with the head 3 welded thereon.

is mounted in a cradle I88 with the spuds 32 projecting downwardly. One of the spuds is disposed in a recess I8'I in the cradle I88, whereby it may reciprocate freely therein for a purpose to be described, and the other spud 32 has projected thereinto, a pin I88 mounted on a carriage I88 reciprocable in ways II8 on the cradle by'a screw III, which may be rotated in any suitable manner, for example by a handle I I2.

' slightly less diameter than rod has a head Th cradle I88 is supported adjacent to the head stock II3 of a lathe or like machine having a rotating spindle II4. In the preferred aror a chuck thereon, is provided with a taper socket I IS. A tool shaft one end I I1 and at the other end having a co-axial stem H8. The shank III is inserted into the taper socket II5 with the tool shaft II8 disposed coaxially within the body I, and with the stem H8 projecting outwardly through the central opening in the spud 8, which has previously been welded on the head 3.

The spud opening constitutes a bearing in which the stem I I8 may rotate.

A fly cutter H9 is mounted on the its outer end a cutting point I28, which may be of the type employed for lathe work. The parts illustrating the cutter are shown fragmentarily in F g. 16.

In operation, the shaft H8 is rotated by the spindle II4 ofvthe said machine and the screw III is turned to feed the tool cutting point I28. longitudinally over, or back and forth over, the

interior fin 88, thereby tooling it off and reduc- 55 ing the metal at the weld juncture to a smooth solid metal surface, such that vitreous enamel will flow evenly thereover and adhere thereto.

It is to be observed that the pin I88 inthe tion of preventing the body I from being rotated by the cutting action of the tool, and of reciprocating the body on the cradle I88 to move the work under the tool. During longitudinal movement of the body, the spud 9 moves axially over the stem II8, the spud' opening therefore periorming the joint function of providing a rotawhen thissecond head has been welded on,

a taper shank I35 are such that when I tool shaft I I8, projecting radially therefrom and having on time substantially fit the same.

' rently rotated by ample that described above for rotating the sup- 32 performs the joint functudinally, toward portion of the boiler.

of its inaccessibility,

'working end of the tool to cause it to tool'off the the spuds in the heads.

The body I and the two heads 2 and 3 welded thereto are now in the condition illustrated in Fig. 1'7, in which the interior fin at the head '2 is indicated at 88A, the fin at the head 3 havin been removed. I have solved the very evident problem of removing this fiashfin 88A, in spite by the method and apparatus illustrated diagrammatically in Figs. 17 and The boiler is mounted on a pair of roller supports I'2I-I2I under the left hand end of the boiler as shown in Figs. 1'7 and 18, and upon a similar pair of roller supports I22-I22 under the right hand end of the boiler. One of the rollers I2I is connected by a gear I23 and a, pinion I24 to a driving pulley I25 by which the roller may be rotated to rotate the boiler upon its roller support, by power from any suitable source.

Upon the frame I28, upon which the roller supports are mounted, is provided a head I21 reciprocable in ways I28 by a rotary device I28 connected to the head I21 by a link I38; A tool I3I is provided in the form of a round rod of that of the spud opening in the spud 8 of the head 3. One end of the I32 thereon pivotally connected at I33 to the reciprocatory head I2'I for hinging movement in' vertical planes. The opposite or is formed to have a out- In an intermediate porbent on a curve of rela- The dimensional ting edge I34 thereon. tion of the rod I3I it is tive large radius .as at I35. proportions of the rod I3I and the outer end portion of the rod is disposed substantially coaxial with the boiler the inner end will be in engagement with the inner wall surface of the boiler.

To dispose the cutting point I34 within the boiler the rod may be hinged upwardly around its hinging connection at I33 and the opening of the spud 9 may be telescoped over the cutting point of the tool and the boiler then placed upon the roller supports. The large radius of the curvature at I35 will permit the rod to be projected through the spud opening and at the same When the head I21 is reciprocated, the cutting point I34 will be reciprocated over the 'fin 88A and tool-the same of! down to a solid metal surface over which vitreous enamel will flow evenly and to which it will adhere. As this reciprocatory cutting movement of the tool goes on, the boiler is concurany suitable means, for exporting rollers, whereby the entire fin circumferentially around the boiler will be tooled oil.

The tendency for the boiler to move longithe left as viewed in the drawing, when the longitudinal force of the cutting operation is communicated thereto, may be resisted and prevented by a roller I38 supported on the base I28 and engaging the head 2.

Various means may be provided to hold cutting head of "the tool against the boiler wall fin and not ride thereover. One means would be to dispense with the supporting rollers I22 under the right hand end The weight of the right hand. end portion of the boiler would then be impressed upon the right rod i3I at the engagement of the spud 9 with the curvature at the hand end of the tooldownwardly around its connection at I33 and force the point I34 of the tool downwardly. This downward force may be supplemented by a roller I31 rolling upon the upper side of the rod' I29 and engaging it with downward force by the action of a spring I38, as an alternative means.

I have found, however, that in most cases, such applied force is unnecessary and in fact, the weight of the right hand end portion of the boiler itself is more than is necessary and therefore in the preferred arrangement some of this weight must be counter-balanced and to this end I provide the following arrangement.

The rollers I22 are rotatably mounted upon an arm I39 pivoted on themain frame at I40 and the free end of the arm I39 is supported upon a spring I, the tension of whi h maybe adjusted by a screw I42. By increasing he tension of the spring I any desired portion/ of the weight of the boiler may be carried by the rollers I22 and thereby the downward force on the rod at the spud may be adiustably varied to cause the tool point I34 to be suitably forced against the wall and to perform its cleaning and tin removing operation. r

The outer fins, 19 and "A are readily accessible, being on the outside of the boiler, and may be removed at any suitable time during the fabricating process and by any suitable means. In Fig. 17 one means is shown comprising a pair of grinding wheels I43 and I44 which may be driven by any suitable well known means and held against the fins I9 and 19A to grind them ofl and reduce the metal to a solid smooth surface over which enamel will completely form and to which it will adhere, while the boiler is being rotated during the removal of the interior fin 80A. The cutting point I 34 of the tool I3I may rest at its point upon the boiler wall as shownin Fig. 17, or it may be formed as in Fig. 19, having a portion I45 inwardly of the cutting point I34, which may rest upon the boiler wall during the reciprocatory movement. While in the foregoing I,have illustrated and described machinery in semi-diagrammatic form for performing various steps of the method of making the boiler embodying my invention, it is believed that those skilled in this art will understand how to supplement this diagrammatic disclosure with the necessary machine details of construction and without the necessity of further invention, if in fact, such additional details are necessary in constructing actual machinery.

An enameled range boiler embodying y invention, as described above and as illustrated in Fig. 1 has improved qualities which are not susceptible of illustration in a drawing, particularly in the esthetlc quality of its appearance, its outside completely thereover surface throughout being in unbroken, jointless. smooth, lustrous surface of vitreous enamel of any desired color or mixed pattern of color known to the vitreous enameling art.

My invention is not limited to the exact details of construction nor to the exact elements f the method and of the machinery illustrated and described above. Changes and modifications" may be made therein without departing from the spirit of my invention or sacrificing its advantages and which come within the scope of the appended claims.

I claim:

1. The method of fabricating a sheet metal range boiler which includes forming a sheet metal tubular boiler body and a pair of sheet metal heads having tubular edge portions, disposing the edge portion of one head in abutting relation with one end of the body and integrally welding it thereto by flash welding, tooling off the interior flash fin to a surface by a tool projected into the opposite open end of the body, providing a perforation in said head, disposing the edge portion of the other head in abutting relation with the other end of the body and integrally welding it thereto by flash welding, tooling oil the interior flash fin of the last named welding operation to a surface by a tool projected through the said perforation, causing the said surfaces to be sufficiently smooth for vitreous enamel to flow and adhere thereto, and coating the entire inside surface of the boiler including said tooled surfaces with vitreous enamel.

2. The method of fabricating a sheet metal range boiler which includes: forming a sheet metal tubular body and a pair sheet metal heads having tubular edge portions; disposing the edge portion of one head in abutting relation with one end of the body and integrally welding it thereto by flash welding; tooling off the interior flash fin to a surface by a tool projected into the opposite open end of the body; providing a central perforation in said head; disposing the edge portion of the other head in abutting relation with the other end of the body and integrally welding it thereto by flash welding; inserting through the said perforation an elongated tool having a cutting edge on its end portion; disposing the cutting edge adiacent the flash lin of the said other head; reciprocating the tool while concurrently rotating the body and heads to cause the tool cutting edge to remove the flash fin of the said head to a surface; causing the said surfaces to be sufllciently smooth for vitreous enamel to flow completely thereover and adhere thereto; and

coating the entire inside surface of the boiler including said tooled surfaces with vitreous enamel.

Joinsa nonnsacx. 

